package com.baidu.unbiz.fluentvalidator.util;

/**
 * Preconditions to check data and throws exception
 *
 * @author zhangxu
 */
public final class Preconditions {

    private Preconditions() {
    }

    /**
     * Ensures the truth of an expression involving one or more parameters to the calling method.
     *
     * @param expression a boolean expression
     *
     * @throws IllegalArgumentException if {@code expression} is false
     */
    public static void checkArgument(boolean expression) {
        if (!expression) {
            throw new IllegalArgumentException();
        }
    }

    /**
     * Ensures the truth of an expression involving one or more parameters to the calling method.
     *
     * @param expression   a boolean expression
     * @param errorMessage the exception message to use if the check fails; will be converted to a string using
     *                     {@link String#valueOf(Object)}
     *
     * @throws IllegalArgumentException if {@code expression} is false
     */
    public static void checkArgument(boolean expression, Object errorMessage) {
        if (!expression) {
            throw new IllegalArgumentException(String.valueOf(errorMessage));
        }
    }

    /**
     * Ensures the truth of an expression involving one or more parameters to the calling method.
     *
     * @param expression           a boolean expression
     * @param errorMessageTemplate a template for the exception message should the check fail. The message is formed
     *                             by replacing each
     *                             {@code %s} placeholder in the template with an argument. These are matched by
     *                             position - the first
     *                             {@code %s} gets {@code errorMessageArgs[0]}, etc. Unmatched arguments will be
     *                             appended to the
     *                             formatted message in square braces. Unmatched placeholders will be left as-is.
     * @param errorMessageArgs     the arguments to be substituted into the message template. Arguments are converted
     *                             to strings using
     *                             {@link String#valueOf(Object)}.
     *
     * @throws IllegalArgumentException if {@code expression} is false
     * @throws NullPointerException     if the check fails and either {@code errorMessageTemplate} or {@code
     *                                  errorMessageArgs} is null (don't
     *                                  let this happen)
     */
    public static void checkArgument(boolean expression, String errorMessageTemplate,
                                     Object... errorMessageArgs) {
        if (!expression) {
            throw new IllegalArgumentException(format(errorMessageTemplate, errorMessageArgs));
        }
    }

    /**
     * Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters
     * to the calling method.
     *
     * @param expression a boolean expression
     *
     * @throws IllegalStateException if {@code expression} is false
     */
    public static void checkState(boolean expression) {
        if (!expression) {
            throw new IllegalStateException();
        }
    }

    /**
     * Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters
     * to the calling method.
     *
     * @param expression   a boolean expression
     * @param errorMessage the exception message to use if the check fails; will be converted to a string using
     *                     {@link String#valueOf(Object)}
     *
     * @throws IllegalStateException if {@code expression} is false
     */
    public static void checkState(boolean expression, Object errorMessage) {
        if (!expression) {
            throw new IllegalStateException(String.valueOf(errorMessage));
        }
    }

    /**
     * Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters
     * to the calling method.
     *
     * @param expression           a boolean expression
     * @param errorMessageTemplate a template for the exception message should the check fail. The message is formed
     *                             by replacing each
     *                             {@code %s} placeholder in the template with an argument. These are matched by
     *                             position - the first
     *                             {@code %s} gets {@code errorMessageArgs[0]}, etc. Unmatched arguments will be
     *                             appended to the
     *                             formatted message in square braces. Unmatched placeholders will be left as-is.
     * @param errorMessageArgs     the arguments to be substituted into the message template. Arguments are converted
     *                             to strings using
     *                             {@link String#valueOf(Object)}.
     *
     * @throws IllegalStateException if {@code expression} is false
     * @throws NullPointerException  if the check fails and either {@code errorMessageTemplate} or {@code
     *                               errorMessageArgs} is null (don't
     *                               let this happen)
     */
    public static void checkState(boolean expression, String errorMessageTemplate,
                                  Object... errorMessageArgs) {
        if (!expression) {
            throw new IllegalStateException(format(errorMessageTemplate, errorMessageArgs));
        }
    }

    /**
     * Ensures that an object reference passed as a parameter to the calling method is not null.
     *
     * @param reference an object reference
     *
     * @return the non-null reference that was validated
     *
     * @throws NullPointerException if {@code reference} is null
     */
    public static <T> T checkNotNull(T reference) {
        if (reference == null) {
            throw new NullPointerException();
        }
        return reference;
    }

    /**
     * Ensures that an object reference passed as a parameter to the calling method is not null.
     *
     * @param reference    an object reference
     * @param errorMessage the exception message to use if the check fails; will be converted to a string using
     *                     {@link String#valueOf(Object)}
     *
     * @return the non-null reference that was validated
     *
     * @throws NullPointerException if {@code reference} is null
     */
    public static <T> T checkNotNull(T reference, Object errorMessage) {
        if (reference == null) {
            throw new NullPointerException(String.valueOf(errorMessage));
        }
        return reference;
    }

    /**
     * Ensures that an object reference passed as a parameter to the calling method is not null.
     *
     * @param reference            an object reference
     * @param errorMessageTemplate a template for the exception message should the check fail. The message is formed
     *                             by replacing each
     *                             {@code %s} placeholder in the template with an argument. These are matched by
     *                             position - the first
     *                             {@code %s} gets {@code errorMessageArgs[0]}, etc. Unmatched arguments will be
     *                             appended to the
     *                             formatted message in square braces. Unmatched placeholders will be left as-is.
     * @param errorMessageArgs     the arguments to be substituted into the message template. Arguments are converted
     *                             to strings using
     *                             {@link String#valueOf(Object)}.
     *
     * @return the non-null reference that was validated
     *
     * @throws NullPointerException if {@code reference} is null
     */
    public static <T> T checkNotNull(T reference, String errorMessageTemplate,
                                     Object... errorMessageArgs) {
        if (reference == null) {
            // If either of these parameters is null, the right thing happens anyway
            throw new NullPointerException(format(errorMessageTemplate, errorMessageArgs));
        }
        return reference;
    }

    /**
     * Substitutes each {@code %s} in {@code template} with an argument. These are matched by position: the first
     * {@code %s} gets {@code args[0]}, etc. If there are more arguments than placeholders, the unmatched arguments will
     * be appended to the end of the formatted message in square braces.
     *
     * @param template a non-null string containing 0 or more {@code %s} placeholders.
     * @param args     the arguments to be substituted into the message template. Arguments are converted to strings
     *                 using
     *                 {@link String#valueOf(Object)}. Arguments can be null.
     */
    // Note that this is somewhat-improperly used from Verify.java as well.
    static String format(String template, Object... args) {
        template = String.valueOf(template); // null -> "null"

        // start substituting the arguments into the '%s' placeholders
        StringBuilder builder = new StringBuilder(template.length() + 16 * args.length);
        int templateStart = 0;
        int i = 0;
        while (i < args.length) {
            int placeholderStart = template.indexOf("%s", templateStart);
            if (placeholderStart == -1) {
                break;
            }
            builder.append(template.substring(templateStart, placeholderStart));
            builder.append(args[i++]);
            templateStart = placeholderStart + 2;
        }
        builder.append(template.substring(templateStart));

        // if we run out of placeholders, append the extra args in square braces
        if (i < args.length) {
            builder.append(" [");
            builder.append(args[i++]);
            while (i < args.length) {
                builder.append(", ");
                builder.append(args[i++]);
            }
            builder.append(']');
        }

        return builder.toString();
    }

}
